But more often than not, a squealing sound is a sign that the battery backup is dead. Unless you have a way of confirming that the battery backup noise is simply coil whine, you should get a replacement. Naturally, you should first consult an expert. They will tell you whether you need to replace the entire unit or just the battery.
Battery banks should be silent, save for a fan if it's a very large one. Any other noise means it's likely not functioning correctly, and has the potential to explode/go up in flames at any time, in use or not. Voltage converters and regulators can making a hissing sound which might change with what is plugged into it.
Aside from beeping, UPS battery backups sometimes emit a high-pitched noise. Depending on your UPS model, that noise might be an alarm that’s been triggered. Or, it could be the typical high-pitched sound coming from the internal battery as it charges. How Do I Reset My Battery Backup?
Simply starting a car while the inverter is hooked to the battery is enough to send the inverter screaming in some cases due to the instantaneous voltage dump to get the car powered up. You might also have loose cables where the cords attach to the back of the inverter or where they connect to the battery terminals or cigarette lighter socket.
If your battery backup has automatic voltage regulation, you will hear a click whenever the backup boosts or reduces the input voltage. Therefore, clicking isn’t necessarily a problem. While your particular backup may also generate a clicking sound whenever it detects a voltage spike. It could also click because the relay is broken.
Many battery backups hum when they are active. For the most part, this is normal. A UPS may hum because it is charging its batteries or carrying out a self-test. The humming may also originate from the fan. Battery Backup Buzzing Noise – Why? Buzzing is another sound that might be normal, especially if it is coming from the power transformer.